WAUSAU - A former Wausau paramedic on Friday pled not guilty to charges he sexually assaulted a woman while treating her in an ambulance.

Clifford Heiser, 33, pled not guilty to all counts against him in a court appearance at the Marathon County Courthouse. The former paramedic and firefighter was charged with two felonies — one count of third-degree sexual assault and one count of misconduct in public office — along with two counts of misdemeanor fourth-degree sexual assault.

Police began investigating the case last month after a 29-year-old female patient said she was groped while riding in a Wausau Fire Department ambulance to a local hospital. According to the criminal complaint, the woman told investigators that a male paramedic molested her genitals and sucked on her breast in the ambulance.

Wausau police arrested Heiser after receiving DNA results related to the investigation. Heiser’s saliva was found on the woman’s right breast, according to the complaint.

The Fire Department placed Heiser on administrative leave after learning of the investigation, but he later resigned. He had been with the department for four years.

Heiser is free on a $25,000 signature bond.

In September when Heiser was charged, Wausau Fire Chief Tracey Kujawa said the department was considering putting video cameras in the back of ambulances.

“We realize that we have violated the trust of our community, but are going to work diligently to regain and repair that trust,” she said.